CN106163700B

CN106163700B - Fe-Co alloy powder, method for producing same, antenna, inductor, and EMI filter

Info

Publication number: CN106163700B
Application number: CN201580017354.XA
Authority: CN
Inventors: 后藤昌大; 吉田贵行
Original assignee: Dowa Electronics Materials Co Ltd
Current assignee: Dowa Electronics Materials Co Ltd
Priority date: 2014-03-31
Filing date: 2015-03-27
Publication date: 2020-09-04
Anticipated expiration: 2035-03-27
Also published as: JP6632702B2; TWI675114B; WO2015152048A1; EP3127634B1; US20180169752A1; KR102290573B1; EP3127634A1; JP2019085648A; JP2015200018A; CN106163700A; US11103922B2; JP6471015B2; TW201542838A; EP3127634A4; KR20160140777A

Abstract

Provided is an Fe-Co alloy powder suitable for an antenna, which has a high saturation magnetization σ s and a controlled coercive force Hc, and which has extremely large μ' and sufficiently small tan (μ). In the method, an oxidizing agent is introduced into an aqueous solution containing Fe ions and Co ions to form nuclei, and when a precursor having Fe and Co as components is deposited and grown, Co in an amount of 40% or more of the total Co amount used in the deposition reaction is added to the aqueous solution at a time after the initiation of the nuclei formation and before the completion of the deposition reaction to obtain a precursor, and then the dried product of the precursor is reduced to obtain Fe-Co alloy powder. The Fe-Co alloy powder has an average particle diameter of 100nm or less, a coercive force Hc of 52.0 to 78.0kA/m, and a saturation magnetization σ s of 160Am²More than kg.

Description

Fe-Co alloy powder, method for producing same, antenna, inductor, and EMI filter

Technical Field

The present invention relates to a metal magnetic powder which is advantageous for improving the relative permeability in a band of several hundred MHz to several GHz, and a method for producing the same.

Background

In recent years, electronic devices using radio waves of several hundreds MHz to several GHz as communication means, such as various portable terminals, have become widespread. As a small antenna suitable for these devices, a planar antenna having a conductor plate and a radiation plate arranged in parallel thereto is known. In order to achieve further miniaturization of such an antenna, it is effective to dispose a magnetic material having a high magnetic permeability between the conductor plate and the radiation plate. However, since conventional magnetic materials have a large loss in a high frequency band of several hundreds MHz or more, a planar antenna using a magnetic material has been becoming popular. For example, patent documents 1 and 2 disclose metal magnetic powder having a real part μ' of a high complex relative permeability, but a sufficient improvement effect is not necessarily obtained for a loss coefficient tan (μ) of the complex relative permeability which is an index of a magnetic loss.

Patent document 3 discloses a technique of increasing magnetic anisotropy and reducing loss coefficient tan (μ) by making the axial ratio (major axis/minor axis) of Fe — Co alloy powder particles relatively large.

Documents of the prior art

Patent document

Patent document 1 Japanese laid-open patent publication No. 2011-

Patent document 2 Japanese laid-open patent application No. 2010-103427

Patent document 3 Japanese laid-open patent publication No. 2013-236021

Disclosure of Invention

Problems to be solved by the invention

In order to miniaturize the high-frequency antenna, a magnetic material having a large μ 'and a small loss coefficient tan (μ) ═ μ "/μ' is advantageous. Here, μ' is a real part of the complex relative permeability, and μ ″ is an imaginary part of the complex relative permeability. For the improvement of μ', it is effective to increase the saturation magnetization σ s of the metal magnetic powder. In general, it is found that σ s tends to increase with an increase in the content ratio of Co in the Fe — Co alloy powder. However, in the conventional general production method, when producing an Fe — Co alloy powder having a high Co content, there is a problem that the so-called μ' does not sufficiently increase regardless of the increase in σ s.

The purpose of the present invention is to provide Fe-Co alloy powder suitable for an antenna, which has a high saturation magnetization σ s, a controlled coercive force Hc, an extremely large μ' and a sufficiently small tan (μ), and to provide an antenna using the same.

Means for solving the problems

In order to achieve the above object, the present invention provides Fe-Co alloy powder having an average particle diameter of 100nm or less, a coercive force Hc of 52.0 to 78.0kA/m, and a saturation magnetization σ s (Am)²/kg) 160Am²More than kg. The σ s satisfies, for example, the following expression (1) in the relationship with the molar ratio of Co/Fe.

σs≥50[Co/Fe]+151…(1)

Here, [ Co/Fe ] means the molar ratio of Co to Fe in the chemical composition of the powder.

The Co/Fe molar ratio of the Fe-Co alloy powder is, for example, 0.15 to 0.50. The average axial ratio (average major axis/average minor axis) of the particles constituting the powder is preferably greater than 1.40 and less than 1.70.

When a molded body prepared by mixing the powder with an epoxy resin at a mass ratio of 90:10 is subjected to magnetic measurement, the Fe-Co alloy powder preferably has properties such that the real part μ ' of the complex relative permeability is 2.50 or more and the loss coefficient tan (μ) of the complex relative permeability is less than 0.05 in 1GHz, and further has properties such that the real part μ ' of the complex relative permeability is 2.80 or more and the loss coefficient tan (μ) of the complex relative permeability is less than 0.12 in 2GHz, and tan (μ) can be controlled to less than 0.10, and further preferably has properties such that the real part μ ' of the complex relative permeability is 3.00 or more and the loss coefficient tan (μ) of the complex relative permeability is less than 0.30 in 3GHz, as the electrical resistance of the powder, the volume resistivity of 1.0 × 10 is measured by the double ring electrode method according to JIS K6911, while applying a load of 1.0g of metal powder between electrodes while applying a voltage of 10V between the electrodes at a load of 25MPa (8kN)⁸Omega cm or more is preferable.

Further, a method for producing the Fe — Co alloy powder includes the steps of:

a step of introducing an oxidizing agent into an aqueous solution containing Fe ions and Co ions to form nuclei, and, when a precursor having Fe and Co as components is deposited and grown, adding Co in an amount of 40% or more of the total amount of Co used in the deposition reaction to the aqueous solution at a time after the initiation of the formation of the nuclei and before the completion of the deposition reaction to obtain a precursor (precursor formation step), a step of heating the dried precursor to 250 to 650 ℃ in a reducing gas atmosphere to obtain a metal powder having an Fe-Co alloy phase (reduction step), and a step of forming a metal powder having a Fe-Co alloy phase by heating the metal powder in a reducing gas atmosphere to 250 to 650 ℃, (reduction step),

A step of forming an oxidation protective layer on the surface layer part of the reduced metal powder particles (stabilization step),

If necessary, the heating treatment at 250 to 650 ℃ in a reducing gas atmosphere and the treatment of the stabilizing step which is continued to the heating treatment are carried out 1 or more times (repeating steps of reducing and stabilizing).

In the precursor forming step, the total amount of Co used in the precipitation reaction and the Co/Fe molar ratio are more preferably in the range of 0.15 to 0.50. If necessary, the rare earth element (Y also operates as a rare earth element) is present in the aqueous solution, and the above-described nuclei can be generated. By changing the addition amount of the rare earth element added before the generation of the nuclei, the axial ratio of the obtained precursor and the finally obtained particles constituting the metal magnetic powder can be changed. Furthermore, 1 or more of rare earth elements (Y is also operated as a rare earth element), Al, Si, and Mg are present in an aqueous solution, and the above-mentioned precipitation growth can be performed.

Further, the present invention provides an antenna formed by using the above-mentioned Fe-Co alloy powder. Particularly, an antenna having a molded body formed by mixing the Fe — Co alloy powder and the resin composition in a component and receiving, transmitting, or transmitting a radio wave having a frequency of 430MHz or more is suitable. Also provided are an inductor and an EMI filter formed by using the Fe-Co alloy powder.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the saturation magnetization σ s of the Fe — Co alloy powder can be significantly improved more than that of the conventional powder when compared with the same Co content. The increase in coercive force Hc accompanying the increase in Co content is also suppressed. The improvement of σ s and the suppression of Hc are extremely advantageous for the improvement of the real part μ' of the complex relative permeability, which is important as high-frequency characteristics. Further, according to the present invention, it is possible to appropriately control the axial ratio of the powder particles, and an increase in the magnetic loss tan (μ) is suppressed. Therefore, the present invention contributes to miniaturization and high performance of the high-frequency antenna and the like. The present invention contributes to miniaturization and high performance of high-frequency components such as not only high-frequency antennas but also inductors and EMI filters.

Drawings

FIG. 1 is a graph showing the relationship between the total Co/Fe molar ratio and the saturation magnetization σ s.

FIG. 2 is a graph showing the relationship between the total Co/Fe molar ratio and the coercive force Hc

Detailed Description

As described above, when particles having a high Co content ratio are produced by the conventional method for producing Fe-Co alloy powder, it is not possible to sufficiently increase μ' regardless of whether the saturation magnetization σ s is increased. As a result of detailed studies, it was found that when particles having a high Co content ratio are produced by a conventional production method, the axial ratio of the particles becomes large, and the magnetic anisotropy increases, whereby the resonance frequency shifts to the high frequency side, and μ' cannot be sufficiently increased. Since magnetic anisotropy is closely related to coercive force Hc, and Hc becomes large when the magnetic anisotropy becomes large, it is important to control the coercive force Hc so as not to become larger than necessary while increasing σ s in order to sufficiently improve μ' as magnetic properties necessary for a magnetic material. On the other hand, when the coercive force Hc is too small, tan (μ) now becomes large, and the loss during use of the antenna increases. From the viewpoint of tan (μ), it is important to control the coercivity Hc so as not to become too small.

As a result of detailed studies, the inventors found that, when a precursor is precipitated and grown in an aqueous solution and the precursor is subjected to reduction firing to obtain Fe — Co alloy magnetic powder, if a method is employed in which a part of Co used in the precipitation reaction is added to the solution in the middle of the process of precipitation and growth of the precursor, the saturation magnetization σ s can be significantly improved without an excessive increase in the coercive force Hc. As a result, while tan (μ) is suppressed to be low, μ' can be significantly increased. The present invention has been completed based on such findings.

Magnetic powder of metal

[ chemical composition ]

In the present specification, the content of Co in the Fe-Co alloy powder is represented by the molar ratio of Co to Fe. This molar ratio is referred to as "Co/Fe molar ratio". In general, saturation magnetization σ s tends to increase with an increase in the molar ratio of Co/Fe. According to the present invention, higher σ s than the conventional general Fe-Co alloy powder is obtained when the same Co/Fe molar ratio is compared. The σ s improving effect is obtained in a wide range of the Co content. For example, Fe-Co alloy powder having a Co/Fe molar ratio of 0.05 to 0.80 can be used. In the case of high-frequency antennas and the like, the Co/Fe molar ratio is preferably 0.15 or more, more preferably 0.20 or more, in consideration of the application where a high σ s is required. In order to obtain a high σ s, it is desirable to contain Co in a large amount, but since excessive Co content causes an increase in cost, the Co/Fe molar ratio is desirably 0.70 or less, more preferably 0.60 or less, and still more preferably 0.50 or less. According to the present invention, even when the molar ratio of Co/Fe is set to 0.40 or less, or further set to 0.35 or less, a high σ s can be obtained.

The metal element other than Fe and Co may contain 1 or more of rare earth elements (Y is also operated as a rare earth element), Al, Si, and Mg. The rare earth element, Si, Al, and Mg are elements added as necessary in a conventionally known process for producing a metal magnetic powder, and the contents of these elements are also acceptable in the present invention. As the element added to the metal magnetic powder, Y is typically mentioned. The molar ratio of rare earth element/(Fe + Co) may be 0 to 0.20, and more preferably 0.001 to 0.05, relative to the total molar ratio of Fe and Co. The Si/(Fe + Co) molar ratio may be set to 0 to 0.30, and more preferably 0.01 to 0.15. The Al/(Fe + Co) molar ratio may be set to 0 to 0.20, and more preferably 0.01 to 0.15. The Mg/(Fe + Co) molar ratio may be set to 0 to 0.20.

[ particle diameter ]

The particle diameter of the particles constituting the metal magnetic powder can be determined by Transmission Electron Microscope (TEM) observation. The diameter of the smallest circle of the particles on the encircled TEM image is defined as the diameter (major axis) of the particles. The diameter thereof is a diameter including an oxidation protective layer covering the periphery of the metal shell. The average value of the diameters of the randomly selected 300 particles can be the average particle diameter of the metal magnetic powder. In the present invention, the powder having an average particle diameter of 100nm or less is used. On the other hand, since ultrafine powder having an average particle size of less than 10nm is accompanied by an increase in production cost and a decrease in workability, it is usually sufficient to set the average particle size to 10nm or more.

[ axial ratio ]

In a certain particle on a TEM image, the length of the longest portion measured in the orthogonal direction to the above-mentioned "major axis" is referred to as the "minor axis", and the ratio of the major axis/minor axis is referred to as the "axial ratio" of the particle. The average axial ratio "of the powder can be determined as follows. In TEM observation, the "major axis" and the "minor axis" were measured for 300 randomly selected particles, and the average of the major axes and the average of the minor axes of all the particles to be measured were referred to as the "average major axis" and the "average minor axis", respectively, and the ratio of the average major axis to the average minor axis was referred to as the "average axial ratio". The average axial ratio of the Fe-Co alloy powder according to the present invention is desirably in the range of more than 1.40 and less than 1.70. If 1.40 or less, the imaginary part μ ″ of the complex relative permeability becomes large due to the decrease in the shape magnetic anisotropy, which is disadvantageous in applications where a decrease in the loss coefficient (μ) is important. On the other hand, if the average axial ratio exceeds 1.70, the effect of improving the saturation magnetization σ s tends to be small, and the advantage is reduced in applications where improvement of the real part μ' of the complex relative permeability is emphasized.

[ powder characteristics ]

The coercive force Hc is preferably 52.0 to 78.0 kA/m. If Hc is too low, tan (μ) becomes large in the characteristic of the frequency of 430MHz or more, and the loss increases when the antenna is used. On the other hand, if Hc is too high, this causes a decrease in the real part μ' of the complex relative permeability in the high-frequency characteristic. In this case, the effect of increasing μ' due to the increase in σ s is undesirable because it kills the two. Hc is more preferably less than 70.0 kA/m. The coercivity can be controlled to the above range by the method of adding Co described later.

Saturation magnetization σ s (Am) of Fe-Co magnetic powder according to the present invention²/kg) in a reaction withThe molar ratio of Co/Fe satisfies the following formula (1).

σs≥50[Co/Fe]+151…(1)

The metal magnetic powder satisfying the formula (1) exhibits a higher σ s in a smaller amount of Co added than a conventional general Fe — Co alloy powder, and is excellent in maintenance cost in terms of saving the amount of Co used, which is more expensive than Fe. In addition, Fe — Co powder satisfying the formula (1) and having the coercive force Hc adjusted in the above range is not conventionally available, and is particularly advantageous for improving μ' in high frequency characteristics. In high frequency applications such as planar antennas, it is preferable to adjust σ s to 160Am²More than kg. σ s ratio 160Am²When the/kg is smaller, μ' becomes smaller, and the effect of downsizing when used in an antenna becomes smaller. In addition, σ s is typically at 200Am²The content may be in the range of not more than kg. By adopting the Co addition method described later, σ s satisfying the expression (1) can be realized.

In addition, it is also possible to obtain a compound satisfying the following formula (2) or satisfying the following formula (3) in place of the above formula (1).

σs≥50[Co/Fe]+157…(2)

σs≥50[Co/Fe]+161…(3)

As other powder characteristics, the BET specific surface area is preferably 30 to 70m²The density of TAP is 0.8-1.5 g/cm³The metal magnetic powder preferably has a delta sigma s of 15% or less before and after a test in which the metal magnetic powder is held in an air environment at a temperature of 60 ℃ and a relative humidity of 90% for 1 week, the delta sigma s representing the rate of change of sigma s before and after the test, wherein delta sigma s (%) is calculated by (sigma s before the test-sigma s after the test)/sigma s × 100 before the test, and the volume resistivity when the metal magnetic powder is measured by sandwiching 1.0g between electrodes and applying a voltage of 10V while applying a vertical load of 25MPa (8kN) according to the double ring electrode method of JIS K6911 is 1.0 × 10 for the insulation⁸Omega cm or more is preferable.

[ permeability, dielectric constant ]

The permeability and dielectric constant exhibited by the Fe — Co alloy powder can be evaluated using a ring-shaped sample prepared by mixing the Fe — Co alloy powder and a resin at a mass ratio of 90: 10. As the resin used at this time, a known thermosetting resin typified by an epoxy resin and a known thermoplastic resin can be used. When such a molded article is produced, the real part μ' of the complex relative permeability is preferably 2.50 or more and the loss coefficient tan (μ) of the complex relative permeability is less than 0.05 in 1GHz, and more preferably, the loss coefficient tan (μ) is 2.70 or more and the tan (μ) is less than 0.03. The tan (. mu.) is preferably as small as possible, but may be adjusted to be generally in the range of 0.005 or more.

Also, the Fe-Co alloy powder according to the present invention exhibits excellent magnetic characteristics also in the frequency region exceeding 1 GHz. For example, when the above-mentioned molded article is exemplified as a 2GHz high-frequency characteristic, a powder having a property that μ' is 2.80 or more and tan (μ) is less than 0.12 or less than 0.10 is suitable. Similarly, when high frequency characteristics of 3GHz are exemplified, a powder having properties of μ' of 3.00 or more and tan (μ) of 0.300 or less to 0.250 or less is more preferable.

In particular, according to the present invention, it is possible to produce and separate an Fe — Co alloy powder that exhibits extremely excellent high-frequency characteristics such as 1GHz μ ' of 3.50 or more, tan (μ) of less than 0.025, 2GHz μ ' of 3.80 or more, tan (μ) of less than 0.12, and 3GHz μ ' of 4.00 or more, and tan (μ) of less than 0.30.

Method for producing

The Fe — Co magnetic powder can be produced by the following steps.

[ precursor Forming Process ]

An oxidizing agent is introduced into an aqueous solution in which Fe ions and Co ions are dissolved to form nuclei, thereby allowing precursors having Fe and Co as components to grow by precipitation. However, Co in an amount corresponding to 40% or more of the amount of Co used in the precipitation reaction is added to the aqueous solution at a time after the initiation of the nucleation and before the completion of the precipitation reaction. For example, when the total amount of Co used in the precipitation reaction is 0.30 in terms of Co/Fe molar ratio, Co is added in an amount of 40% or more thereof, that is, in an amount of 0.30 × (40/100) × (0.12 or more in terms of Co/Fe molar ratio, at a time after the initiation of the nucleation and before the completion of the precipitation reaction. In the following, an aqueous solution before the initiation of nucleation (i.e., before the initiation of introduction of the oxidizing agent) is referred to as a "reaction stock solution", and a period before the initiation of nucleation is referred to as an "initial stage". The time after the initiation of the formation of the nuclei (i.e., after the initiation of the introduction of the oxidizing agent) and before the completion of the precipitation reaction is referred to as "intermediate stage", and the operation of adding a water-soluble substance to the liquid and dissolving the substance in the intermediate stage is referred to as "intermediate addition".

The reaction solution must contain at least Fe ions. As the aqueous solution in which Fe ions are present, a 2-valent Fe ion-containing aqueous solution obtained by neutralizing a water-soluble iron compound (iron sulfate, iron nitrate, iron chloride, etc.) with an aqueous solution of alkali hydroxide (NaOH, KOH, etc.) or an aqueous solution of alkali carbonate (sodium carbonate, ammonium carbonate, etc.) is suitable. In the reaction liquid, it is preferable that a part of Co is already dissolved in the whole Co used in the precipitation reaction. As the Co source, a water-soluble cobalt compound (cobalt sulfate, cobalt nitrate, cobalt chloride, or the like) can be used. As the oxidizing agent, an oxygen-containing gas such as air, hydrogen peroxide, or the like can be used. The reaction liquid is aerated with an oxygen-containing gas or an oxidant substance such as hydrogen peroxide to form nuclei of the precursor. Thereafter, the introduction of the oxidizing agent is continued, and an Fe compound or a Co compound is precipitated on the surface of the nuclei to grow precursor particles. The precursor may be mainly composed of a crystal having a structure in which a part of the Fe side of the iron oxyhydroxide or the iron oxyhydroxide is replaced with Co.

Conventionally, Co is usually dissolved in the entire amount in the initial stage of the reaction liquid. However, in the conventional Co addition method, the saturation magnetization σ s increases and the coercivity Hc increases as the Co content increases. The reason for this is that the Co addition facilitates the precipitation in the longitudinal direction, and the effect of the shape magnetic anisotropy due to the increase in the axial ratio is considered to be large. The increase in coercive force Hc causes a decrease in the real part μ' of the complex relative permeability. In order to improve the high frequency characteristics, it is desired to develop a new technique that can increase the saturation magnetization σ s while suppressing the increase in the coercive force Hc. As a result of detailed studies, the inventors found that by adding a part of Co in the middle, the increase in coercive force Hc and the saturation magnetization σ s can be suppressed and significantly improved.

Part of the total Co content is added separately in the middle, whereby the Co content in the initial stage can be reduced. This makes it possible to precipitate and grow the precursor in a state where the amount of dissolved Co is small, and to suppress an increase in the axial ratio. It is known that, to some extent, even if Co is added in a large amount after the growth of the precursor particles, unlike the growth from the stage of the seed crystal, the decrease in the preferential precipitation in the long diameter direction is reduced. Thus, even if the total Co content is the same, precursor particles having a smaller axial ratio can be obtained. It is considered that the Co concentration of the particles in the peripheral portion is higher than that in the central portion, but it is considered that the concentration of Fe and Co is homogenized by atomic diffusion during reduction firing. The amount of Co added in the course of the reaction is effective to be 40% or more of the total amount of Co used in the precipitation reaction.

The method of adding Co in the middle of the process can be carried out by directly charging the water-soluble cobalt compound or by charging a solution in which Co is dissolved in advance. The addition may be carried out by a batch method or a continuous method. It is preferable that Co is added in an amount of 40% or more of the total amount of Co in the course of the precipitation reaction after the time when 10% of the total amount of Fe used in the precipitation reaction is oxidized (i.e., when the precipitation reaction is consumed), and it is more preferable that Co is added in an amount of 40% or more of the total amount of Co in the course of the precipitation reaction after the time when 20% of the total amount of Fe used in the precipitation reaction is oxidized.

If necessary, 1 or more of rare earth elements (Y is also operated as a rare earth element), Al, Si, and Mg can be in a state of existing in an aqueous solution to cause precipitation growth of a precursor. The timing of addition of these elements may be any of the initial stage, the intermediate stage, the initial stage, and the intermediate stage. As the supply source of these elements, each water-soluble compound may be used. Examples of the water-soluble rare earth element compound include iridium sulfate, iridium nitrate, and iridium chloride. Examples of the water-soluble aluminum compound include aluminum sulfate, aluminum chloride, aluminum nitrate, sodium aluminate, and potassium aluminate. Examples of the water-soluble silicon compound include sodium silicate, sodium orthosilicate, potassium silicate, and the like. Examples of the water-soluble magnesium compound include magnesium sulfate, magnesium chloride, and magnesium nitrate. The content of these additive elements is preferably 0.20 or less in the molar ratio of rare earth element/(Fe + Co), and may be controlled to 0.001 to 0.05. The molar ratio of Al/(Fe + Co) is preferably 0.20 or less, and may be controlled to be in the range of 0.01 to 0.15. The Si/(Fe + Co) molar ratio is preferably 0.30 or less, and may be controlled to be in the range of 0.01 to 0.15. The Mg/(Fe + Co) molar ratio is preferably in the range of 0.20 or less, and may be controlled in the range of 0.01 to 0.15.

[ reduction Process ]

The dried precursor obtained by the above method is heated in a reducing gas atmosphere to obtain a metal powder having an Fe — Co alloy phase. The reducing gas is typically hydrogen gas. The heating temperature may be set to a range of 250 to 650 ℃, and more preferably 500 to 650 ℃. The heating time is adjusted within the range of 10-120 min.

[ stabilizing procedure ]

When the metal powder after the reduction step is exposed to the atmosphere as it is, it may be rapidly oxidized. The stabilization step is a step of forming an oxidation protective layer on the particle surface while avoiding rapid oxidation. The atmosphere to which the reduced metal powder is exposed is an inert gas atmosphere, and the oxidation reaction of the surface layer portion of the metal powder particle is carried out at 20 to 300 ℃, more preferably 50 to 300 ℃ while increasing the oxygen concentration in the atmosphere. In the case where the stabilization step is performed in the same furnace as the reduction step, after the reduction step is completed, the reducing gas in the furnace may be replaced with an inert gas, and the oxidation reaction of the surface layer portion of the particles may be performed while introducing an oxygen-containing gas into the inert gas atmosphere in the temperature range. The metal powder may be transferred to another heat treatment apparatus to perform a stabilization process. After the reduction step, the metal powder may be continuously subjected to a stabilization step while being moved by a conveyor belt or the like. In either case, it is important that the metal powder is transferred to the stabilization step without being exposed to the atmosphere after the reduction step. As the inert gas, 1 or more gas components selected from a lean gas and a nitrogen gas can be applied. As the oxygen-containing gas, pure oxygen gas and air can be used. Steam may be introduced simultaneously with the oxygen-containing gas. The steam has an effect of densifying the oxide film. The metal magnetic powder is maintained at an oxygen concentration of 30 to 300 ℃, preferably 50 to 300 ℃, and is finally set to 0.1 to 21 vol%. The introduction of the oxygen-containing gas may be carried out continuously or intermittently. In the initial stage of the stabilization step, the oxygen concentration is more preferably 1.0 vol% or less for 5.0min or more.

[ repeating steps of reduction and stabilization ]

The stabilizing step may be followed by a heating treatment at 250 to 650 ℃ in a reducing gas atmosphere and a subsequent treatment of the stabilizing step 1 or more times. This can increase the effect of improving the saturation magnetization σ s by Co addition.

Antenna

The Fe-Co alloy powder of the present invention can be used as a constituent material of an antenna. For example, a planar antenna having a conductor plate and a radiation plate arranged in parallel thereto may be used. The structure of the planar antenna is disclosed in fig. 1 of patent document 3, for example. The Fe-Co alloy powder of the present invention is extremely useful as a magnetic material for an antenna for transmitting and receiving radio waves of 430MHz or higher. Particularly, the present invention is more effective when applied to an antenna used in a frequency band of 700MHz to 6 GHz.

The Fe — Co alloy powder according to the present invention is used as a magnetic material for the antenna by being formed into a molded body mixed with a resin composition. As the resin, a known thermosetting resin or thermoplastic resin may be used. For example, the thermosetting resin may be selected from phenol resins, epoxy resins, unsaturated polyester resins, isonitrile acid ester compounds, melamine resins, urea resins, silicone resins, and the like. As the epoxy resin, any of monoepoxy compounds, polyvalent epoxy compounds, or a mixture of these may be used. The monoepoxy compound and the polyvalent epoxy compound are various compounds exemplified in patent document 3, and these compounds can be used by appropriately selecting them. The thermoplastic resin may be selected from polyvinyl chloride resins, ABS resins, polypropylene resins, polyethylene resins, polystyrene resins, acrylonitrile styrene resins, acrylic resins, polyethylene terephthalate resins, polyphenylene ether resins, polysulfone resins, polyarylate resins, polyetherimide resins, polyether ether ketone resins, polyether sulfone resins, polyamide resins, polyamideimide resins, polycarbonate resins, polyacetal resins, polyethylene terephthalate resins, polyether ether ketone resins, polyether sulfone resins, Liquid Crystal Polymers (LCP), fluorine resins, urethane resins, and the like.

The mixing ratio of the Fe — Co alloy powder and the resin is preferably 30/70 or more and 99/1 or less, more preferably 50/50 or more and 95/5 or less, and further preferably 70/30 or more and 90/10 or less, as represented by the mass ratio of the metal magnetic powder/resin. When the amount of the resin is too small, a molded body cannot be formed, and when the amount is too large, desired magnetic properties cannot be obtained.

Examples

EXAMPLE 1

[ preparation of reaction stock solution ]

About 800mL of a solution was prepared by mixing 1mol/L of an aqueous ferrous sulfate solution and 1mol/L of an aqueous cobalt sulfate solution so that the molar ratio of Fe to Co became 100:10, and about 1L of a solution containing Fe, Co and Y was prepared by adding 0.2mol/L of an aqueous iridium sulfate solution so that the molar ratio of Y/(Fe + Co) became 0.026. 2600mL of pure water and 350mL of ammonium carbonate solution were added to a 5000mL beaker, and the mixture was stirred with a temperature controller while maintaining the temperature at 40 ℃ to obtain an ammonium carbonate aqueous solution. The ammonium carbonate solution contains Fe in a solution corresponding to the concentrations of Fe, Co and Y²⁺With carbonic acid CO₃ ^2-Adjusted to 3 equivalents. Adding the solution containing Fe, Co and Y into the ammonium carbonate aqueous solution to prepare a reaction stock solution. In this example, the Co/Fe molar ratio was 0.10 at the completion of the preparation in the initial stage (reaction liquid).

[ precursor formation ]

3mol of the above reaction solution was addedH of/L₂O₂5mL of the aqueous solution was used to form iron oxyhydroxide nuclei. Thereafter, the solution was heated to 60 ℃ to thereby make the total Fe present in the reaction liquid²⁺Until 40% of the solution was oxidized, air was blown into the solution at a blowing rate of 163 mL/min. In this case, the necessary ventilation amount is previously determined by a preliminary experiment. Thereafter, a 1mol/L aqueous cobalt sulfate solution containing Co in an amount such that the Co/Fe molar ratio becomes 0.10(═ 10 mol%) was added midway to the total amount of Fe in the reaction liquid. After the addition of Co in the middle, 0.3mol/L of an aluminum sulfate aqueous solution was added so that the Al/(Fe + Co) molar ratio relative to the total amount of Fe and Co (including Co added in the middle) became 0.055, and air was blown at a blowing rate of 163mL/min until the oxidation was completed (i.e., until the precursor formation reaction was completed). The precursor-containing slurry thus obtained was filtered, washed with water, and then dried in air at 110 ℃ to obtain a dried product (powder) of the precursor. In this example, the molar ratio of ready-to-add Co/Fe was 0.10 during the addition, and the total molar ratio of ready-to-add Co/Fe was 0.20. The amounts of Co added to complete the preparation are shown in Table 1.

[ reduction treatment ]

The dried precursor was placed in a barrel capable of aeration, the barrel was placed in a through-type reduction furnace, and reduction treatment was carried out by maintaining the furnace at 630 ℃ for 40min while flowing hydrogen gas.

[ stabilization treatment ]

After the reduction treatment, the atmosphere gas in the furnace was changed from hydrogen to nitrogen, and the temperature in the furnace was reduced to 80 ℃ at a temperature reduction rate of 20 ℃/min in a state where the nitrogen gas flowed in. Thereafter, as an initial gas for the stabilization treatment, a gas in which nitrogen gas and air were mixed (oxygen concentration was about 0.17 vol%) was introduced into the furnace so that the volume ratio of nitrogen gas to air became 125/1 to start the oxidation reaction at the surface layer portion of the metal powder particles, and thereafter the mixture ratio of air was gradually increased to continuously introduce a final gas mixture (oxygen concentration was about 0.80 vol%) in which the volume ratio of nitrogen gas to air became 25/1 into the furnace, thereby forming an oxide protective layer at the surface layer portion of the particles. In the stabilization treatment, the temperature was maintained at 80 ℃ and the gas introduction flow rate was maintained almost constant.

Through the above steps, a test powder having a magnetic phase of the Fe-Co alloy phase was obtained.

[ compositional analysis ]

The composition of the test powder was analyzed by an ICP emission analyzer. The results are shown in Table 1.

[ average particle diameter, average axial ratio ]

The average particle diameter and the average axial ratio of the test powder were measured by the above-described method of TEM observation. The results are shown in Table 1.

[ volume resistivity ]

The volume resistivity of the test powder was measured by a method of sandwiching 1.0g of the test powder between electrodes by a double ring electrode method according to JIS K6911, applying a voltage of 10V while applying a vertical load of 13 to 64MPa (4 to 20 kN). For the measurement, a high resistivity meter Highrensta UP (MCP-HT450) manufactured by Mitsubishi chemical Analytech, Mitsubishi chemical corporation, Milliki resistivity measurement Unit (MCP-PD 51), and a high resistance powder measurement software device manufactured by the same corporation were used. The results are shown in Table 2.

[ BET specific surface area ]

The BET specific surface area was determined by the BET one-point method using 4Sobus manufactured by Yuasaionic. The results are shown in Table 2.

[ TAP Density ]

The TAP density was measured by putting a test powder into a glass sample cell (5mm diameter. times.40 mm height) and tapping 200 times with the TAP height set at 10 cm. The results are shown in Table 2.

[ magnetic characteristics and weather resistance of powder ]

As the magnetic properties (bulk properties) of the test powder, the coercive force Hc (kA/m) and saturation magnetization σ s (Am) were measured using a VSM device (VSM-7P, manufactured by Toyobo industries, Ltd.) under an external magnetic field of 795.8kA/m (10kOe)²In terms of weather resistance,/kg), angular ratio SQ., the metal magnetic powder was evaluated by the rate of change Δ σ s of σ s before and after the test by holding the powder in an air environment at 60 ℃ and 90% relative humidity for 1 week, Δ σ s was calculated by (σ s before the test- σ s after the test)/σ s × 100 before the test, and the results are shown in table 3.

In Table 3, the values on the right side of the above expression (1), and σ s (Am)²The difference between/kg) and the value on the right side of the formula (1). When the difference between σ s and the value on the right side of expression (1) is 0 or positive, expression (1) is satisfied.

[ measurement of magnetic permeability and dielectric constant ]

The test powder and an epoxy resin (TSC, manufactured by TOYOBO CO., LTD.; one-pack epoxy resin B-1106) were weighed at a mass ratio of 90:10, and kneaded using a vacuum stirring-defoaming mixer (V-mini 300, manufactured by EME Co., Ltd.) to obtain a paste in which the test powder was dispersed in the epoxy resin. The paste was dried on a hot plate at 60 ℃ for 2 hours to prepare a composite of metal powder and resin, and then granulated into powder to prepare composite powder. 0.2g of the composite powder was placed in an eggplant-shaped container, and a load of 9800N (1Ton) was applied thereto by a hammer press, whereby a ring-shaped compact having an outer diameter of 7mm and an inner diameter of 3mm was obtained. The molded article was measured for the real part μ 'and imaginary part μ ″ of the complex relative permeability and the real part' and imaginary part of the complex relative permittivity at 0.1 to 4.5GHz using a network analyzer (available from Agilent Technologies, E5071C) and a coaxial S-parameter method sample holder (available from kanto electronics co., CSH2-APC7, sample size:, Φ 7.0mm- Φ 3.04mm × 5mm), and the loss coefficient tan (μ) ═ μ "/μ ″ of the complex relative permittivity and the loss coefficient tan () of the complex relative permittivity were determined. In table 4, the results of these in 1GHz, 2GHz, and 3GHz are illustrated.

EXAMPLES 2 and 3

An experiment was carried out under the same conditions as in example 1, except that the molar ratio of ready-to-add Co/Fe added in the process was increased to 0.15 (example 2) and 0.20 (example 3), respectively. Production conditions and results are shown in tables 1to 4 (the same for each example below) in the same manner as in example 1.

EXAMPLE 4

An experiment was carried out under the same conditions as in example 2 except that the air blowing rate after the addition of Co in the middle of the growth of the precursor was decreased to 81.5 mL/min.

EXAMPLE 5

An experiment was carried out under the same conditions as in example 3, except that the air blowing rate after the addition of Co in the middle of the growth of the precursor was decreased to 40.8 mL/min.

EXAMPLE 6

An experiment was carried out under the same conditions as in example 5, except that the molar ratio of ready-to-add Co/Fe added in the process was increased to 0.25.

EXAMPLE 7

An experiment was carried out under the same conditions as in example 5 except that the molar ratio of preparatory Co/Fe added in the course of the initial period was increased to 0.15 and the molar ratio of preparatory Co/Fe added in the course of the period was decreased to 0.15.

EXAMPLE 8

An experiment was performed under the same conditions as in example 4, except that the reduction treatment and the stabilization treatment were performed again 1 time in the same furnace after the stabilization treatment. In this case, the conditions of the reduction treatment and the stabilization treatment at the 2 nd time are the same as those of the reduction treatment and the stabilization treatment at the 1 st time, respectively (the same in examples 9 and 10 below).

EXAMPLE 9

After the stabilization treatment, an experiment was performed under the same conditions as in example 5, except that the reduction treatment and the stabilization treatment were performed again 1 time in the same furnace.

EXAMPLE 10

After the stabilization treatment, an experiment was performed under the same conditions as in example 6, except that the reduction treatment and the stabilization treatment were performed again 1 time in the same furnace.

EXAMPLE 11

An experiment was carried out under the same conditions as in example 9, except that the temperature of the stabilization treatment was changed to 70 ℃.

EXAMPLE 12

An experiment was carried out under the same conditions as in example 10, except that the temperature of the stabilization treatment was changed to 70 ℃.

EXAMPLE 13

An experiment was carried out under the same conditions as in example 12 except that the air blowing rate after the addition of Co in the middle of the growth of the precursor was decreased to 34.6 mL/min.

EXAMPLE 14

In the precursor formation process, the liquid temperature after the formation of the nuclei of the iron oxyhydroxide was set to 50 ℃ until all Fe was present in the reaction liquid²⁺The experiment was carried out under the same conditions as in example 13 except that the blowing rate of air into the solution until oxidation was 106mL/min for 40% of the total amount.

EXAMPLE 15

An experiment was carried out under the same conditions as in example 14, except that the molar ratio of preparatory Co/Fe to be added in the initial stage was 0.08 and the molar ratio of preparatory Co/Fe to be added in the middle was 0.27.

EXAMPLE 16

An experiment was carried out under the same conditions as in example 13 except that the molar ratio of preparatory Co/Fe at the initial stage was 0.08, the molar ratio of preparatory Co/Fe added midway was 0.27, and the liquid temperature in the air blowing from the time of adding Co midway to the completion of oxidation was changed from 60 ℃ to 55 ℃ in the precursor formation process.

Comparative examples 1to 5

In comparative examples 1, 2, 3, 4 and 5, experiments were carried out under the same conditions as in example 1 except that the initial preparation completion Co/Fe molar ratios were 0.05, 0.10, 0.15, 0.20 and 0.25, respectively, and no Co was added in the process.

[ Table 1]

[ Table 2]

UR: lower than the range

[ Table 3]

FIG. 1 shows the relationship between the total Co/Fe molar ratio (analytical value) and the saturation magnetization σ s in each of the above examples. In each of the examples in which Co was added halfway in the process of growing the precursor, it was found that the effect of increasing σ s accompanying the increase in Co content was greater than that of the comparative example in which Co was not added halfway. Fig. 1 shows the boundary line of the above equation (1). When the precursor is grown by a method of adding Co in the middle, the effect of increasing σ s remarkably as satisfying the formula (1) is obtained. In the drawings of the examples, the blank square symbols are examples 8 to 10 in which 2 sets of the total of the reduction treatment and the stabilization treatment are repeated, the blank triangle symbols are examples 11 to 13 in which 2 sets of the total of the reduction treatment and the stabilization treatment are repeated at a temperature of 70 ℃, and the blank inverted triangle symbols are examples 14 to 16 (the same as in fig. 2 described later). With respect to these, a further significant σ s increasing effect is obtained.

FIG. 2 shows the relationship between the total Co/Fe molar ratio (analysis value) and the coercive force Hc of each example. In the examples in which Co was added halfway in the process of growing the precursor, it was found that the increase in coercive force Hc was suppressed as compared with the comparative examples in which Co was not added halfway.

The permeability of the examples is significantly improved in the real part μ' of the complex relative permeability of 1to 3GHz as compared with the comparative examples. This is considered to be an effect of suppressing the increase of Hc while σ s is high in the Fe-Co alloy powders of the examples. In addition, the loss coefficient tan (μ) can be suppressed low regardless of whether μ' in the example is increased or not. This is considered to be an effect of controlling an appropriate range in which the average axial ratio of the Fe-Co alloy powder is not excessively small by adding Co in the middle.

Claims

1. Fe-Co alloy powder suitable for antennas, inductors and EMI filters, which has an average particle size of 100nm or less, a coercive force Hc of 52.0-78.0 kA/m, and a saturation magnetization σ s of 160Am²More than kg.

2. The Fe-Co alloy powder for antenna, inductor and EMI filter according to claim 1, wherein the saturation magnetization σ sAm is²The molar ratio of Co to Fe satisfies the following formula (1):

σs≥50[Co/Fe]+151…(1)

3. The Fe-Co alloy powder for antenna, inductor and EMI filter according to claim 1 or 2, wherein the Co/Fe molar ratio is 0.15 to 0.50.

4. The Fe-Co alloy powder suitable for antennas, inductors, and EMI filters according to claim 1 or 2, wherein the average axial ratio of particles constituting the powder, i.e., the average major axis/average minor axis ratio is greater than 1.40 and less than 1.70.

5. The Fe-Co alloy powder suitable for antennas, inductors and EMI filters according to claim 1 or 2, wherein the volume resistivity measured by a double ring electrode method according to JIS K6911 by sandwiching 1.0g of the metal powder between electrodes and applying a voltage of 10V while applying a vertical load of 25MPa or 8kN is 1.0 × 10⁸Omega cm or more.

6. The Fe-Co alloy powder suitable for an antenna, an inductor and an EMI filter according to claim 1 or 2, wherein when a molded body prepared by mixing the powder and an epoxy resin at a mass ratio of 90:10 is subjected to magnetic measurement, the powder has a property that a real part μ' of a complex relative magnetic permeability is 2.50 or more and a loss coefficient tan (μ) of the complex relative magnetic permeability is less than 0.05 at 1 GHz.

7. The Fe-Co alloy powder suitable for an antenna, an inductor and an EMI filter according to claim 1 or 2, wherein when a molded body prepared by mixing the powder and an epoxy resin at a mass ratio of 90:10 is subjected to magnetic measurement, the powder has a property that a real part μ' of a complex relative magnetic permeability is 2.80 or more and a loss coefficient tan (μ) of the complex relative magnetic permeability is less than 0.12 at 2 GHz.

8. The Fe-Co alloy powder suitable for an antenna, an inductor and an EMI filter according to claim 1 or 2, wherein when a molded body prepared by mixing the powder and an epoxy resin at a mass ratio of 90:10 is subjected to magnetic measurement, the powder has a property that a real part μ' of a complex relative magnetic permeability is 3.00 or more and a loss coefficient tan (μ) of the complex relative magnetic permeability is less than 0.30 at 3 GHz.

A method for producing an Fe-Co alloy powder, comprising:

a precursor forming step: introducing an oxidizing agent into an aqueous solution containing Fe ions and Co ions to form nuclei, and in growing a precursor having Fe and Co as components by precipitation, adding Co to the aqueous solution in an amount of 40% or more of the total amount of Co used in the precipitation reaction, i.e., the sum of the amount of Co added before the introduction of the oxidizing agent and the formation of nuclei is started and the amount of Co added after the introduction of the oxidizing agent and the formation of nuclei is started and before the precipitation reaction is ended, to obtain a precursor,

a reduction step of heating the dried precursor to 250 to 650 ℃ in a reducing gas atmosphere to obtain a metal powder having an Fe-Co alloy phase,

and a stabilization step of forming an oxidation protective layer on the surface layer part of the reduced metal powder particles.

10. The method for producing an Fe-Co alloy powder according to claim 9, wherein in the precursor formation step, the ratio of the amount of all Fe ions added to the reaction liquid to the amount of all Co ions used in the precipitation reaction is set to a Co/Fe molar ratio in the range of 0.15 to 0.50.

11. A method for producing an Fe — Co alloy powder according to claim 9 or 10, wherein in the precursor forming step, the nuclei are generated in a state where the rare earth element is present in an aqueous solution.

12. A method for producing an Fe-Co alloy powder according to claim 9, wherein in the precursor forming step, the precipitation growth is performed in a state where 1 or more of the rare earth elements, Al, Si, and Mg are present in an aqueous solution.

13. The method for producing an Fe-Co alloy powder according to claim 9, wherein the method comprises, after the stabilizing step, a step of repeating the reducing and stabilizing by performing the heating treatment at 250 to 650 ℃ in a reducing gas atmosphere and the subsequent treatment in the stabilizing step 1 or more times.

14. An antenna formed using the Fe-Co alloy powder according to any one of claims 1to 8.

15. An antenna for receiving, transmitting, or transmitting a radio wave having a receiving frequency of 430MHz or more, comprising a molded body in which the Fe-Co alloy powder according to any one of claims 1to 8 is mixed with a resin composition.

16. An inductor formed by using the Fe-Co alloy powder according to any one of claims 1to 8.

An EMI filter formed by using the Fe-Co alloy powder according to any one of claims 1to 8.